Print some output to the user when we can't find the content after a few seconds

If I do `ipfs get ` while the IPFS daemon is running I basically get no output, never (or at least for several minutes in my local test). It would be nice to tell *something* to the user so it doesn't (understandably) assume that the command is dead or that it is taking a lot of time to download what was supposed to be a small file (when we actually can't even find it).

For example,

```
ipfs get Qmfoo
# (X seconds go by and we don't find Qmfoo)
Can't find Qmfoo, looking...
# (This can now go forever, but at least we now
# know that it's having trouble finding the hash.)
```